Dual effect: High NADH levels contribute to efflux-mediated antibiotic resistance but drive ROS lethality

In light of the antibiotic crisis, emerging strategies to sensitize bacteria to available antibiotics should be explored. Several studies on the mechanisms of killing suggest that bactericidal antibiotic activity is enforced through the generation of reactive oxygen species (ROS lethality hypothesis). Here, we artificially manipulated the redox homeostasis of the model opportunistic pathogen Pseudomonas aeruginosa using specific enzymes that catalyze either the formation or oxidation of NADH. Increased NADH levels led to the activation of antibiotic efflux pumps and high levels of antibiotic resistance. However, higher NADH levels also resulted in increased intracellular ROS and amplified antibiotic killing. Our results demonstrate that growth inhibition and killing activity are mediated via different mechanisms. Furthermore, the profound changes in bioenergetics produced low virulence phenotypes characterized by reduced inter-bacterial signaling controlled pathogenicity traits. Our results pave the way for a more effective infection resolution and add an anti-virulence strategy to maximize chances to combat devastating P. aeruginosa infections while reducing the overall use of antibiotics. Differential expression of P. aeruginosa cells expressing either a NADH oxidase or a formate dehydrogenase and compared to a empty plasmid control